1. Field of the Invention
This invention relates generally to semiconductor processing and, more specifically, to treating residues in semiconductor processing chambers. In particular, this invention relates to a method for neutralizing and/or removing residues left by metal source gases, such as titanium tetrachloride (TiCl4), on semiconductor processing chamber walls.
2. Description of the Related Art
In semiconductor manufacturing operations, semiconductor devices are formed using various processes, including deposition of conducting and insulating layers on semiconductor substrates. Continuing miniaturization of integrated circuits has required the development and use of methods for depositing new and different types of metal and metal-based layers on semiconductor substrates. These new types of layers include metal and metal oxide combinations that have been developed for use as both insulating and conducting layers. Among the most widely used of these new types of layers are titanium-based layers, such as titanium silicide (TiSi2) and titanium (Ti). Other titaniumbased layers, including titanium oxide combinations, have also been contemplated. Thus, a wide variety of metal-based conductors and insulators are utilized in the art.
Chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD) processes are used to deposit metal-based layers. Often the deposition process of such metal-based layers includes the use of a metal source known as a precursor. For example, CVD processes that employ titanium precursor deposition gases, such as titanium tetrachloride (TiCl4), have often been employed to deposit these layers. For example, TiSi2 has been deposited in a cold wall CVD reactor process by reacting TiCl4 with a silicon source deposition gas, such as silane (SiH4).
Metal deposition processes carried out in semiconductor processing chambers may leave contaminant deposits of metal precursor on the walls of a processing chamber. For example, in cold wall CVD deposition processes employing a TiCl4 precursor, a residue derived from TiCl4 is often deposited on the reactor chamber walls. In such a cold wall plasma CVD process for the deposition of TiSi2 from TiCl4 and SiH4, the primary deposition reaction occurs at the surface of the semiconductor substrate which is heated to a reaction temperature, typically above about 300xc2x0 C. However, the walls of a cold wall CVD reactor are typically maintained at temperatures ranging from around ambient to a maximum of about 250xc2x0 C. At lower temperatures, TiCl4 does not participate in the primary reaction and may instead deposit residues on the CVD chamber walls. These TiCl4-derived residues are usually strongly bound to the interior of the reactor chamber and may be difficult to remove, remaining bound to the chamber walls even after long xe2x80x9cpump downsxe2x80x9d or evacuations of the semiconductor chamber. These deposits are also prone to causing accelerated corrosion of aluminum chamber walls and typically react readily with moisture-laden air, generating a white xe2x80x9csmokexe2x80x9d when a reactor chamber is opened. Particles from this xe2x80x9csmokexe2x80x9d may eventually settle from the air to coat surfaces within a fabrication clean room.
Although plasma cleaning methods exist which may be used for removing TiCl4-derived residues from reactor chamber walls, these methods suffer from several disadvantages. First, plasma cleaning methods are typically directional or anisotropic, meaning only a portion of the interior surfaces of a reactor chamber are accessible for plasma cleaning. As a result, plasma cleaning may only be effective in removing TiCl4-derived deposits from some parts of the reactor chamber, leaving TiCl4-derived residue strongly bound to other areas of the chamber which are not directly exposed to the plasma. This remaining residue retains its potential for reacting with the atmosphere the next time the reactor chamber is opened. In addition, plasma cleaning methods require the installation of special equipment into a reactor chamber and may not always be available or desirable.
Consequently, a need exists for a method that is effective in neutralizing or removing metal-based deposits from substantially all areas of a semiconductor processing chamber. In particular, a need exists for a method of neutralizing and/or removing reactive TiCl4-derived residues present in a cold wall CVD reactor chamber.
The present invention concerns a method for treating metal-based residues in semiconductor processing chambers with treatment gases that act to convert residues to substantially stable and/or removable materials.
This invention in one respect is a method for treating a metal-based residue in a semiconductor processing chamber by introducing a treatment gas into the processing chamber capable of interacting with the metal-based residue to form a substantially stable and removable treatment product.
This invention in another respect is a method for treating a metal-based residue present in a semiconductor processing chamber by introducing a treatment gas into the processing chamber under conditions effective to cause the treatment gas to interact with the metal-based residue to form a substantially stable and removable treatment product, and removing at least a portion of the treatment product from the semiconductor processing chamber.
This invention in a further respect is a method for neutralizing and removing a residue comprising at least one chloride of titanium from a cold wall CVD reactor chamber by providing and introducing an ammonia treatment gas into the cold wall CVD chamber so that an adduct salt of at least one chloride of titanium and ammonia is formed, and removing at least a portion of the adduct salt from the cold wall CVD reactor.
This invention in yet another respect is a method for neutralizing a metal-based residue in a semiconductor processing chamber by introducing a treatment gas into the processing chamber that is capable of neutralizing the metal-based residue.
The present invention offers advantages over methods previously employed to treat contaminants and residues in semiconductor processing chambers, including for example, the capability of neutralizing reactive metal-based residues that are strongly bound to surfaces of semiconductor processing chambers in areas not accessible to other cleaning methods, and converting these residues to substantially stable materials that may be easily removed from the chamber walls.